Production of ammonia synthesis feed gas



June 10, 1958 w. M. s'rRA'rFoRD PRODUCTION OF AMMONIA SYNTHESIS FEED GASFiled nec. 2s, 1955 2 Sheets-Shea?l l I I I I I I I I I I I I I I I I II I I I I I I I I Il. I I I I I I I I I I |.I.I|

2 Sheets-Sheet 2 .oxide with concomitant production of hydrogen.

United States Patent O OF AIVIMONIA SYNTHESIS FEE PRODUCTION D GASApplication December 23, 1955, Serial N0. 554,964

8 Claims. (Cl. 252-376) This invention relates to a process for theproduction of ammonia synthesis feed gas. In one of its more specificaspects, this invention relates to an improved method for the productionof a mixture of hydrogen and nitrogen in the required proportions forthe synthesis of ammonia.

This is a continuation-in-part of my application Serial No. 406,108,tiled January 26, 1954, now abandoned, entitled Production of AmmoniaSynthesis Feed Gas.

In the synthesis of ammonia, a feed gas containing three parts hydrogenby volume per part of nitrogen is required. Various methods have beendevised for the production of hydrogen for ammonia synthesis and forblending the hydrogen with nitrogen in the required proportions.

Fossil carbonaceous fuels and their derivatives, i. e. normally liquidand normally gaseous hydrocarbons and solid fuels, such as coal or coke,are most useful for the production of ammonia synthesis feed gas. Thesefuels may be used for the production of hydrogen by reaction with free,or uncombined, oxygen, optionally in the presence of steam. `Partialoxidation of a fossil carbonaceous fuel produces a mixture of carbonmonoxide and hydrogen. The carbon monoxide may then be reacted withsteam to produce carbon dioxide and hydrogen; one volume of hydrogen isproduced for each volume of carbon monoxide reacted. Following theaddition of nitrogen and the removal of carbon, dioxide and Iotherundesired components, ammonia synthesis feedgas is obtained.

The present invention provides an improved process for the production ofammonia synthesis feed gas from fossil carbonaceous fuels. Solid, liquidor -gaseous fuel may be used. In the process of this invention,carbonaceous fuel and free `oxygen are reacted under conditionseffective for the production of near maximum yields of carbon mon- Partof :the fuel is reacted with substantially pure oxygen While anotherpart is reacted with air. Each reaction is conducted fundersubstantially optimum conditions, preferably in separate reaction zones.The same fuel or different fuels may be employed as feed for the airreaction zone and for the oxygenreaction zone.

Preferably the relative proportions of the reactants, i. e. fuel, air,oxygen, and, optionally, steam, employed in the various react-ion zonesare such that the combined products of reaction from all of the reactionzones contain carbon monoxide, hydrogen and nitrogen in relative amountssuch that the Sum of the carbon monoxide and hydrogen by volume isapproximately three times `the nitrogen by volume. The carbon monoxideis subjected to reaction with steam to produce an equivalent amount ofhydrogen following which carbon dioxide and steam are separated from thegas stream leaving a mixture of nitrogen and hydrogen in approximatelyrequired proportions for ammonia synthesis. Undesirable impurities, suchas argon and methane, are preferably removed from the pro-duct gas 'bywashing the nitrogen-hydrogen mixture with substantially pure liquidnitrogen.

The carbonaceous fuel is reacted with :oxygen-containing gas, i. e.oxygen or air, optionally including steam, in

2,838,460 Patented June 10, 1958 ICC a closed, compact reaction zone atan autogenously maintained reaction temperature above about 2,000 F.`and preferably in the range -of 2,200 to 3,200 F. The reaction Zone isfree from packing and catalyst and preferably has near-minimum internalsurface. The reaction may be conducted at atmospheric pressure or at anelevated pressure which may be as high as several hundred pounds persquare inch, e. g. l-00 or 1000 p. s. i. g. Pressures on the order of200 to 600 p. s. i. g. are preferred. The product consists essentiallyof carbon monoxide and hydrogen and contains water vapor and smallamounts of methane and carbon dioxide.

Air, oxygen-enriched air, or substantially .pure oxygen may be employedin the production of carbon monoxide and hydrogen from the fossilcarbonaceous fuel stocks used. Oxygen may be obtained from therectification -of air. Commercial oxygen plants are axailable capable ofdelivering large amounts of high purity oxygen. Commercial oxygen, soproduced, usually contains in excess of mol percent oxygen.

The amount of oxygen supplied to lthe reaction zone is limited so thatnear-maximum yield of carbon monoxide and hydrogen is obtained while atthe same time maintaining the desired reaction temperature. Total oxygenrequlrements of the operation are somewhat in excess `of that amountstoichiometrically required to convert all of the carbon in the fuelfeed to carbon monoxide. Oxygen requirements for various fuels differ.With natural gas and oxygen as sole reactants, the amount of oxygenyrequired is on the order of 5 to 2O percent in excess of thetheoretical; with air and coke oven gas, lfor example, as much aspercent excess :oxygen may be required. With oil as fuel, from about 0.6to about 1.3 pounds of free oxygen and from about 0.2 to about 1.5pounds of steam per pound of oil may be used. An example .of typicalfeed proportions is 0.5 pound steam and 1 pound oxygen per pound of oil.With coal as fuel, from 0.4 to lpound of free (uncombined) oxygen isrequired per pound of coal together with 0.3 to 3 pounds of steam perpound of coal. An example of typical feed proportions for a bituminouscoal is 0.9 pound oxygen and 2 pounds water per pound of coal.

With liquid and solid fuels, steam is preferably also supplied to thegenerator las a reactant. Steam serves the -dual function of limitingthe maximum temperature in the reactor and at the same time suppliesoxygen for `the reaction and produces hydrogen. The steam should beheated to a temperature as high as practical. Preferably the steam ispreheated to atemperat-ure of at least 600 F. and, advantageously, to atemperature of at least 1200 F. Carbon dioxide may be employed togetherwith or in lieu of steam. Generally, however, steam is preferred.Similarly, the other reactants should be preheated to a temperature ashigh as practical. Solid fuels advantageously are preheated bysuspension in lsteam as described hereinafter. Air preferably ispreheated to a temperature of 600 F. or higher. Because of thereactivity of pure oxygen, it is usually preferable to limit the oxygenpreheat temperature to a temperature somewhat less than 600 F.Satisfactory operation may be obtained with no preheatof the oxygen feedstream. Gaseous hydrocarbons may be preheated to temperatures on theorder of 600 to l400 F. Liquid hydrocarbons generally may be heated totemperatures on the order of 600 F.

When solid fuels are employed, the solid fuel particles should notexceed an average diameter of microns and are preferably 40 microns andsmaller in average diameter. Mechanical grinding of the solid fuel issatisfactory; steam jet pulverization of the solid fuel is preferredsince size reduction, preheating and solid material handling is securedsimultaneously with -the'fprovision of steam for the gasificationVprocess. i *i Preferably the fuel and oxygen are separately introducedinto the reaction zone and mixed therein. Introductionof the fuel andoxygen streams through concentric tubes at high velocity, e. g. 100 to200 feet per second, is satisfactory. The reactant streams preferablyare directed away from the reactor walls so that there is no directimpingement thereon, e. g. reactants are introduced axially at one endof a cylindrical reactor ang reaction products are discharged from theopposite en and the gases scrubbed with water for removal of carbon orother solids. Y

Carbon monoxide produced in the gas generation re. actor may be made toyield an equivalent amount of hydrogen by reaction with steam. Theconversion of carbon monoxide to carbon dioxide by reaction with steamto produce additional hydrogen is known as the Reaction products may bequenched with water l water-gas shift reaction. This reaction is usuallyconl ducted at about 750 F. over an iron catalyst. A commercial catalystfor this reaction comprises iron oxide, promoted with oxides ofchromium, potassium, magnesium and aluminum. The lconversion of carbonmonoxide to carbon dioxide by the water-gas shift reaction isessentially complete.

Carbon dioxide may be removed from the product gas-stream following thewater-gas shift reaction step by scrubbing the gas with water or with anamine, e. g. monoethanolamine, or by a combination of these procedures.Residual carbon monoxide may be substantially completely removed fromthe gas stream by scrubbing with an aqueous solution of cuprous ammoniumchloride (Cu(NH3)2Cl) which also removes any remaining carbon dioxide.Various other salts may be used for the removal of carbon monoxide, asis known in the art. Sometimes it is desirable to employ a caustic wash,i. e. Contact between the gas and a solution of sodium hydroxide,following-other purification steps, to remove residual carbon dioxidefrom the gas stream.

The synthesis of ammonia is effected by reacting nitrogen with hydrogenin the presence of a suitable catalyst. 'Ihree volumes of hydrogen arerequired per volume of nitrogen. In the usual commercial processes, theammonia synthesis reaction is conducted at a pressure of severalthousand pounds per square inch, suitably 5000 and higher, and at anelevated temperature, suitably around 950 F. One of the commercialcatalysts is prepared by admixing oxides of potassium and aluminum aspromoters with magnetic iron oxide which is subsequently reduced tometallic iron. In commercial operations, low conversion per pass isobtained, i. e. only a limited amount of the nitrogen-hydrogen mixture-is converted to ammonia each time it passes over the catalyst.Commonly, from 8 to 12 percent of the feed mixture is converted per passover the catalyst. Unconverted nitrogen and hydrogen are recycled.Roughly 90 percent of the feed to the converter represents recycled gas.

Undesirable gases, notably hydrocarbons and inert atmospheric gases,tend to accumulate in the ammonia synthesis gas in the conversionsection. It is customary to purge a portion of the recycled gas streamto prevent build-up in concentration of undesirable gases in theconverter. As a result of this purge, generally only about 85 percent ofthe hydrogen, which has been made and purified at considerable expense,is ultimately converted to ammonia. To prevent this wasteful loss ofhydrogen it is essential that the hydrocarbon content, essentiallymethane, of the feed gas stream be kept at a low value, e. g. belowabout 0.3 mol percent.

The cost of the oxygen from an oxygen plant represents an item ofconsiderable expense in the generation of synthesis gas by partialoxidation. Ordinarily the oxygen plant is designed to supply all of thefree oxygen required for the partial oxidation reactions as aconcentrate of at least 95 percent. purity by volume and hydrogen.

the requisite nitrogen for the ammonia synthesis reaction as aconcentrate containing in excess of 99 percent nitrogen by volume. Whilethis conventional operation is entirely satisfactory from an operationalstandpoint, the process of this invention effects a considerable savingsin oxygen costs. The present process permits generation of a givenamount of ammonia synthesis feed gas with a minimum investment in oxygenfacilities. Alternatively, and quite often more important, thisinvention provides a means for increasing the synthesis gas generationcapacity of an existing plant without increasing the oxygen plantcapacity.

An object of the present invention is to provide an improved process forthe preparation of ammonia synthesis feed gas.

Another object is to provide a process for producing ammonia synthesisfeed gas containing essentially no unreactive gases.

Still another object is to provide a process for producing ammoniasynthesis feed gas by partial oxidation of carbonaceous fuels with aminimum requirement of concentrated oxygen.

A further object is to provide a process for producing ammonia synthesisfeed gas of exceptionally high purity.

The process of this invention will be readily understood from thefollowing description, with reference to the accompanying drawings. Thedrawings are diagrammatie flow sheets illustrating several ways ofcarrying out the process of this invention.

Referring to Figure l, air is rectified in an oxygen plant 6, producingan oxygen-rich fraction and a nitrogen-rich fraction. Oxygen from theoxygen plant is supplied to a plurality of synthesis gas generators 7wherein it is reacted with one or more carbonaceous fuels, e. g. agaseous or liquid hydrocarbon, or a solid fuel, such as coal, to producecarbon `monoxide and In a separate generator 8, which may be identicalwith generators 7, carbonaceous fuel, either the same as or differentfrom that supplied to generators 7, is reacted with air to produce amixture of hydrogen, carbon monoxide and nitrogen.

The eflluent stream from generator 8 is combined with the productstreams from generators 7 to produce a cornposite mixture of carbonmonoxide, hydrogen and nitrogen. The composite mixture is fed to a shiftconverter 9 where the carbon monoxide is reacted with steam to producecarbon dioxide and hydrogen. The eluent from the shift converter is sentto purification system 10 in `which carbon dioxide, and unreacted steamand carbon monoxide are removed from the gas stream. The gas streamleaving the purification system is essentially nitrogen and hydrogen,containing a minor amount of argon (from the air and oxygen supplied tothe generators) and unconverted hydrocarbon (primary methane). A minoramount of methane appears in the product gas from the reactorsregardless of whether a hydrocarbon or a solid carbonaceous fuel isused. The purified gas stream from the nitrogen wash may be sentdirectly to the ammonia synthesis reactors.

In a preferred embodiment, the nitrogen-hydrogen mixture leaving thepurification system 10 is subjected to additional purification to removethe methane and argon from the gas stream. This may be accomplished by anitrogen wash step 11, in which the nitrogen-hydrogen A stream iscontacted with liquid nitrogen obtained from the oxygen plant. Washingthe gas stream with liquid nitrogen condenses out argon and residualhydrocarbons. Any water, carbon dioxide or carbon monoxide notcompletely removed by the purification step 10 is also removed in thenitrogen wash step. The purified ammonia synthesis feed gas leaving thenitrogen wash 11 is a mixture of nitrogen and hydrogen of very highpurity.

Figure 2 illustrates an embodiment wherein at least part of the fossil`carbonaceous fuel is pulverized coal. Pulverized coal is slurried withwater in tank 15 and a heated to form a suspension of coal in steam inheater I6. Oxygen from oxygen plant 6 is supplied to. generator 17wherein it is reacted with the pulverized coal to produce carbonmonoxide and hydrogen. In a. separate generator 18, which may begenerally like generator 17 but of somewhat smaller capacity, ahydrocarbon,

e. g. natural gas or oil, is reacted with -air to producea' mixture ofhydrogen, carbon monoxide and nitrogen. Alternatively, orsupplementally, additional coal slurry from tank 15 may be passedthrough heater 16a to generator 18. v

The product streams from generators 17 and 18 are combining to produce acomposite mixture of car-bon monoxide, hydrogen and nitrogen. Thecomposite mixture is treated in shift converter 9, purification systemand liquid nitrogen wash system 11 `as hereinbefore described to producea mixture of nitrogen and hydrogen of very high purity.

The purity of the gas stream depends to a large extent on the purity ofthe nitrogen available from the oxygen plant. VCommercial oxygen plantsmay be operated to produce nitrogen of over 99.5 volume percent` purity.Nitrogen of at least 99.5 percent purity is preferred in the presentprocess.

Nitrogen may be added to or taken from the gas stream in the nitrogenwash step, depending on the conditions under which the step is operated.If all of the refrigeration required to cool the gas stream (from aboutatmospheric temperature) yto the temperature of liquid nitrogen comesfrom the liquid nitrogen itself, nitrogen will be added to the gasstream in passing through the nitrogen wash. However, the nitrogen washstep may be operated with supplemental refrigeration so that somenitrogen is condensed from the gas stream and the nitrogen content ofthe gas stream reduced.

Gaseous nitrogen may be supplied, as necessary, to the ammonia synthesisfeed gas stream from the oxygen plant.

The operation of my process will be clear from the following exampleswherein several variations of the process are described in detail. Thepressures, temperatures and other operating conditions given therein areto 'be taken as illustrative and. not as hunting. It-Will be evident tothose skilled in the art that other equivalent process steps may besubstituted for the specific steps described in the examples.

EXAMPLE 1v Air is rectified in a commercial oxygen plant to produce anoxygen stream of 95 percent lpurity (by volume) and nitrogen of 99.7percent purity. The oxygen is vsupplied at 295 F. to four flow-typesynthesis gas generators. Natural gas of the following composition isheated to 915 F. and supplied to the generators.

Natural gas v Component: Amount (vol. percent) Methanel 87.1

Ethane 7.9

' Propane and heavier 2.0 Nitrogen 1.9 Carbon dioxide 1.1

ysure of 300 p. s. i. g. A temperature of 2600 F. is yautogenouslymaintained by 'the reaction between the 'oxygen and the natural gas.

Vrate of 239,800 standard cubic feet (at 60 F. and 1 Natural gas is fedat the atmosphere) per hour, -and oxygen, at the rate .of 164,600

ystandard cubic feet per hour. The productgas (on 'a water-free basis)has the following composition.

Synthesis gas (A) Component: Amount (vol. percent) Carbon monoxide 36.0Hydrogen 59.8 Carbon dioxide 2.0 Methane 0.2 Nitrogen and kargon 2.0

Synthesis gas (B) Component: y Amount (vol. percent) Carbon monoxide'15.9 Hydrogen 23.2 Carbon dioxide 2.3 Methane 0.2 Nitrogen and argon58.4

The product gas streams from all the gas generators are mixed and passedto a shift converter where the carbon monoxide is reacted with steam. Inthe shift converter the carbon monoxide is almost completelyconvertedtol carbon dioxide. The shift reactor yemploys an iron catalyst andoperates at about 760 F. The product Ygas from the shift convertercontains approximately 2 percent by volume residual carbon monoxide on adry, carbon dioxide-free basis.

Following the shift converter, the gas is subjected to purification:first, by cooling to condense water, then, by scrubbing withmonoethanolamine solution tov remove carbon dioxide followed byscrubbing with a 10 percent solution of sodium hydroxide. Thepurification steps effeet removal of most of the water, andsubstantially all of the vcarbon dioxide from the gas stream. Theresulting purified gas stream still contains a small amount of carbonmonoxide (l to 2 percent), residual hydrocarbon from the gas generators(0.1 to 0.5 percent) and argon (less than l percent). The argon' entersthe system in the air and oxygen supplied to the generators. Thismixture may be supplied to the ammonia synthesis reactors.

Optionally, and preferably, the gas is further purified by subjectingthe gas stream to a liquid nitrogen wash operation. In this particularexample, the gas, after leaving the caustic scrubber, is cooled to atemperature of about 40 F. while under a pressure of 300 pounds persquare inch gauge. Condensate water is separated. from the gas streamand the partially dried gas then passed through a chemical driercontaining'alumina to reduce the Water content of the gas stream to lessthan 2 parts per million. The dry gas stream is thencooled toapproximately ,-3l5 F. in heatl exchangers and introduced into amultiple plate wash tower where the cooled gas is intimately contactedwith liquid nitrogen of 99.7' percent purity obtained from the airrectification plant. The liquid nitrogen owing down the tower condensesargon, carbon monoxide and methane from the gasstream so that the gasleaving the top of the tower is essentially free from these components.The cold gas from the top of the,

4is conducted at a pressureof approximately k275 pounds per square inchgauge. o

EXAMPLE 2 Biturninous coal, pulverized so that 70 percent is finer than200 mesh, is slurried with water and pumped at about 1200 p. s. i.gjinto a slurry preheating coil wherein it isheated to 1000 F. Theslurry is fed at the rate of .8,111 pounds per hour of coal and 7,812pounds per hour .of waterthrough the preheater wherein the water isconverted into steam.

-, The resulting dispersion of powdered coal and steam is dischargedinto the top of vertical flow-type cylindrical synthesis gas generator Ahaving internal volume of about 40 cubic feet. The reactor length isabout two and one half times its diameter. Bypreheating and dischargingthe coal into the generator with the steam, a highly reactive dispersionof fuel is obtained. Composition of the coal feedin weight percent (drybasis) is as follows:

Component: Weight percent Sulfur 2.59 Nitrogen 1.50 Carbon. 77.29Hydrogen 4.93 Oxygen 5.38 Ash 8.31

Air is rectified in a commercial oxygen plant to produce an oxygenstream of 95 volume percent purity and a nitrogen stream of 99.7 volumepercent purity. The oxygen is supplied at 530 p. s. i. g. and 300 F.into synthesis gas generator A and admixed with the stream of coal andstream within the generator. The oxygen feed rate is 89,617 standardcubic feet per hour. Generator pressure is maintained at 500 p. s. i. g.and temperature at 2,500 F. Molten slag, ungasied coal and product gasare discharged through an opening in the bottom of the generator andquenched with soft water. Product gas of the following volumetriccomposition is separated off at the rate of 304,750 S. C. F. H.(measured on a dry basis).

Component: Volume percent Carbon monoxide 45.3 Hydrogen 36.7 Carbondioxide 14.7

Methane 0.4 Nitrogen 0.9 Monatomic gases 1 1.2 Hydrogen sulfide 0.7Carbonyl sulfide 0.1

1 Rare atmospheric gases (mainly argon).

Additional pulverized coal and soft water are slurried and preheated inthe same way and in the Same proportions as described hereinbefore, thenfed into the top of another vertical flow-type synthesis gas generator,denoted herein as generator B. Generator B has internal volume of about23 cubic feet and a low ratio of internal surface relative to itsvolume. 'Ihe slurry feed rate to generator B is 1367 pounds per hour ofcoal and 1309 pounds per hour of water. Air, preheated to 1,000 F., issupplied at 525 p. s. i. g. and a rate of 87,240 S. C. F. H. togenerator B and admixed with the coal and steam ows at the point oftheir introduction into said generator. Pressure and temperature ingenerator B are the same as those in generator A.

Molten slag and product gas are discharged through `an opening in thebottom of generator B and quenched with soft water. Product gas of thefollowing volumetric composition is produced at the rate of 115,815standard cubic feet per hour (measured on a dry bas-is);

, Y 8V t Component: Volume percent Carbon .monoxide 18.1 Hydrogen 13.0Carbon dioxide 8.6

. Methane 0.2 VNitrogen 59.1 Monatomic gases 0.7 Hydrogen sulfide 0.3

` The product gas streams from generators A and B are mixed and treatedin essentially the same manner as is described in Example 1, i. e.passed with added steam into a shift converter wherein the carbonmonoxide is reacted with steam, cooled, scrubbed free of carbon dioxideand washed with liquid nitrogen for final purification.

Under the above conditions 26,536 S. C. F. H. nitrogen is added to thegas stream in the nitrogen wash tower, and purified ammonia synthesisgas consisting of three volume parts of hydrogen to one volume part ofnitrogen is produced at the rate of 383,640 S. C. F. H. This issuilicient for synthesis of about 103 tons per day of anhydrous ammonia.

EXAMPLE 3 In this case commercial oxygen and slurried bituminous coalare fed to generator A in the same way as is described in Example 2 toproduce an unpuriiied synthesis gas of the same kind, while generator Bis operated on air and natural gas of the composition shown in Example1.

The air andnatural gas, each separately preheated to 1,100" F., are fedto generator B, the natural gas at 'the rate of 20,301 S. C. F. H. andthe air at 89,727

S. C. F. H. to produce 121,961 standard cubic feet per hour of productgas from generator B having composition essentially the same as that ofsynthesis gas B shown in Example 1.

The product gas streams from generators A and B are mixed for subsequentshift conversion of the carbon monoxide in the mixed streams intohydrogen. The mixed streams are treated essentially in the saine manneras is described in Example 1, i. e. subjected to shift conversion withadded steam then cooled, scrubbed free of carbon dioxide and furtherpurified by washing with liquid nitrogen.

Under the above conditions 27,613 S. C. F. H. nitrogen is added to thepurified gasstream in the nitrogen wash tower and purified ammoniasynthesis gas consisting of three volume parts hydrogen and one volumepart nitrogen is produced at the rate of 399,165 S. C. F. H. This issufioient for about 107 tons of anhydrous ammonia. per day.

EXAMPLE 4 In this case commercial oxygen and slurried bituminous coalare fed to generator A the same way as is described in Example 2, toproduce an unpurified synthesis gas of the same kind, while generator Bis operated on air and a cycle fuel oil from refinery operations. Thisoil has an API gravity of 4.5, Saybolt Furol viscosity of 259 at 122 F.,and has the following approximate analysis:

Component: Weight percent Carbon 89.0

Hydrogen 9.0 Nitrogen 1.0 Sulfur 1.0

The oil is preheated, atomized with steam, and reacted with air ingenerator B at 2,630 F. and 500 p. s. i. g. The feed consists of 87,745S. C. F. H. of air, 1,096 lbs. per hour of oil and 331 lbs. per hour ofsteam. The oil and steam mixture enters the generator at 550 F., and theair at F. Raw synthesis gas from generator 9 B, 117,178 S. C. F. H. hasthe following approximate analysis on a dry basis:

Component: Volume percent Hydrogen 16.0 Carbon monoxide 18.0 Carbondioxide 6.6 Nitrogen and argon 59.1 Methane 0.2 Hydrogen sultide 0.1

Product gas streams from generators A and B are mixed for subsequentshift conversion of the carbon monoxide in the mixed streams intohydrogen. The mixed streams are treated essentially in the same manneras described in Example 1, i. e. subjected to shift conversion withadded steam, cooled, scrubbed free of carbon dioxide and furtherpurified by-washing with liquid nitrogen.

Under the above conditions 26,885 S. C. F. H. of nitrogen is added tothe purified gas stream in the nitrogen wash tower and purified ammoniasynthesis gas consisting of three volume parts hydrogen and one volumepart nitrogen is produced at the rate of 388,618 S. C. F. H. This issufficient for about 104 tons of anhydrous ammonia.

It will be evident that the nitrogen wash may be operated, if desired,at a pressure and temperature such that nitrogen is added to the gasstream undergoing treatment or under conditions such that nitrogen isremoved from the gas stream. Gaseous nitrogen is available from theoxygen plant, This gaseous nitrogen may be used, if desired, tosupplement nitrogen from the other sources, i. e. from the air andoxygen introduced into the generators and the nitrogen introduced in thenitrogen wash. Thus, any deficiency in the nitrogen content of the gasstream at the point of discharge from the nitrogen wash tower may bereadily supplied from the oxygen plant. In some instances, it `may bedesirable to control the nal composition of the gas stream by the.addition of small amounts of nitrogen, as required, from the oxygenplant.

The foregoing description and examples relate to preferred operatingconditions for the various feed streams useful in the present inventionprocess. It is to be understood, however, that the operating conditionsare illustrative only and that the process may be operated under otherconditions for example, at higher or lower pressures and temperatures,without departing from the spirit of my invention.

Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

' I claim:

l. A process for the production of a mixtureV of hydrogen and nitrogenin the relative proportions of approximately three volumes of hydrogenper volume of nitrogen which comprises reacting fossil carbonaceous fuelin a first reaction zone with an oxygen-containing gas comprisingsubstantially pure oxygen as the sole source of free oxygen at atemperatureV above about 2250 F. in relative proportions such that thecarbon content of said fuel is substantially completely converted tocarbon monoxide, subjecting additional fossil carbonaceous fuel toreaction with lair in a second reaction zone at a temperature aboveabout 2250 F. in rel-ative proportions such that the carbon content ofsaid fuel is substantially completely converted to carbon monoxide,forming a mixture containing carbon monoxide and nitrogen; combining theproducts of said reactions comprising carbon monoxide and nitrogentogether with any hydrogen concomitantly produced in relativeproportions such that the composite stream contains at least threevolumes of carbon monoxide and hydrogen per volume of nitrogen;subsequently converting carbonl monoxideV in said composite streamsubstantially completely to carbon dioxide by reaction with steamthereby producing hydrogen; and removing steam and carbon oxides fromthe resulting gas stream thereby producing a gaseous mixture of hydrogenand nitrogen containing approxif mately three volumes of hydrogen pervolume of nitrogen.

2. A process according to claim 1 wherein the fuel supplied to at leastone of said reaction zones is a finely divided solid carbonaceous fuel.

3. A process according to claim l wherein the carbonaceous fuel suppliedto at least one of said reaction zones is a hydrocarbon.

4. A process according to claim l in which a pressure of at least p. s.i. g. is maintained in each of said reaction zones.

5. A process for the production of a mixture of hydrogen and nitrogen inthe relative proportions of approximately three volumes of hydrogen pervolume of nitrogen which comprises reacting fossil carbonaceous fuel ina first reaction zone with an oxygen-containing gas comprisingsubstantially pure oxygen as the sole source of free oxygen at atemperature above about 2250 F. in relative proportions such lthat thecarbon content of said fuel is substantially completely converted tocarbon monoxide, subjecting additional fossil carbonaceous fuel toreaction with air in a second reaction zone at a temperature above about2250 F. in relative proportions such that the carbon content of saidfuel is substantially completely converted to carbon monoxide, forming amixture containing carbon monoxide and nitrogen; combining theproducts-of said reactions comprising carbon monoxide and nitrogentogether with any hydrogen concomitantly produced in relativeproportions such that the composite stream contains at leastthreevolumes of carbon monoxide and hydrogen per volume of nitrogen;subsequently converting carbon monoxide in said composite streamsubstantially completely to carbon dioxide by reaction with steamthereby producing hydrogen; removing steam and carbon oxides from theresulting gas stream; thereafter contacting the resulting gas streamwith an excess of liquid nitrogen thereby effecting removal of gasesother than hydrogen and nitrogen therefrom, and adding sucient nitrogento form a mixture of three volumes of hydrogen per volume of nitrogen.

6. A process for the production of a mixture of hydrogen and nitrogen inthe relative proportions of approximately three volumes of hydrogen pervolume of nitrogen which comprises reacting a stream of hydrocarbon withsubstantially pure oxygen at a temperature above about 2250 F. in anunpacked reaction zone in relative proportions such that saidhydrocarbon and oxygen are substantially completely converted to carbonmonoxide and hydrogen; subjecting a second stream of hydrocarbon toreaction with air in a second unpacked reaction zone at a temperatureabove about 2250" F. in relative proportions such that said hydrocarbonand air are substantially completely converted to a mixture of carbonmonoxide, hydrogen and nitrogen; combining the products of saidreactions in relative proportions such that the composite streamcontains at least three volumes of carbon monoxide and hydrogen pervolume of nitrogen; subsequently converting carbon monoxide in saidcornposite stream substantially completely to carbon dioxide by reactionwith steam thereby producing hydrogen; removing steam and carbon oxidesfrom the resulting gas stream; thereafter contacting the resulting gasstream with an excess of liquid nitrogen thereby effecting removal ofgases other than hydrogen and nitrogen therefrom, and adding suicientnitrogen to form a mixture of three volumes of hydrogen per volume ofnitrogen.

7. A process for the production of a mixture of substantially purehydrogen and nitrogen in the relative proportions of approximately threevolumes of hydrogen per volume of nitrogen which comprises separatingair by rectification into an oxygen-rich fraction containing in excessof about 95 volume percent hydrogen and a nitrogen-rich fractioncontaining about 99 volume percent nitrogen, reacting fossilcarbonaceous fuel in a iirst reaction zone at a temperature above about2250 F. with said oxygen-rich fraction in relative proportions such thatthe carbon content of said fuel is substantially completely converted tocarbon monoxide subjecting additional fossil carbonaceous fuel toreaction with air in a second reaction zone at a temperature above about2250 F. in relative proportions such that the carbon content of saidfuel is substantially completely converted to carbon monoxide from amixture comprising nitrogen, carbon oxides, unconverted hydrocarbon andinert atmospheric gases together with any hydrogen concomitantlyproduced in said reactions in relative proportions such that thecomposite stream contains at least three volumes of carbon monoxide andhydrogen per volume of nitrogen subsequently converting carbon monoxidein the resulting mixture substantially completely to carbon dioxide byreaction with steam with the concomitant production of hydrogen removingsteam and carbon oxides from the resulting gas stream contacting theresulting gas stream with an excess of liquid nitrogen from saidnitrogen-rich fraction thereby effecting condensation of carbonmonoxide, unconverted hydrocarbons and inert atmospheric gasestherefrom, and adding suflicient nitrogen to said gas stream to form amixture containing three volumes of hydrogen per volume of nitrogensubstantially free from other gases.

8. A process for the production of a mixture of hydrogen and nitrogen inthe relative proportions of approximately three volumes of hydrogen pervolume of nitrogen which comprises separating air by rectication intofractions comprising an oxygen-rich fraction containing in excess of 95volume percent oxygen and a nitrogenrich fraction containing in excessof about 99 volume percent nitrogen; reacting a stream of hydrocarbonwith said oxygen-rich fraction at a temperature above about 2250" F. inan unpacked reaction zone in relative proportions such that saidhydrocarbon and oxygen are substantially completely converted to carbonmonoxide and hydrogen; subjecting a second stream of hydrocarbon in asecond unpacked reaction zone at a temperature above about 22507 F. toreaction with air in relative proportions such that said hydrocarbon andair are substantially completely converted to a mixture of carbonmonoxide, hydrogen `and nitrogen; combining products of said reactionsin relative proportions such that the composite stream contains at leastthree volumes of carbon monoxide and hydrogen per volume of nitrogen;subsequently converting carbon monoxide in said composite streamsubstantially completely to carbon dioxide by reaction with steam;removing steam and carbon oxides from the resulting gasfstream;thereafter contacting the resulting gas stream wtih said nitrogen-richfraction in liquid phase employing an excess of liquid nitrogen therebyeffecting removal of gases other than hydrogen and nitrogen therefrom;and adding sulicient nitrogen to form a mixture of three volumes ofhydrogen per volume of nitrogen.

References Cited in the file of this patent UNITED STATES PATENTS1,716,813 Casale June 1l, 1929 1,957,744 Wietzel et al May 8, 19342,042,665 Kinzel June 2, 1936 2,582,938 Eastman et al e Jan. 15, 1952FOREIGN PATENTS 231,218 Great Britain Mar. 26, 1925 289,080 GreatBritain July 15, 1929

1. A PROCESS FOR THE PRODUCTION OF A MIXTURE OF HYDROGEN AND NITROGEN INTHE RELATIVE PROPORTIONS OF APPROXIMATELY THREE VOLUMES OF HYDROGEN PERVOLUME OF NITROGEN WHICH COMPRISES REACTING FOSSIL CARBONACEOUS FUEL INFIRST REACTION ZONE WITH AN OXYGEN-CONTAINING GAS COMPRISINGSUSBTANTIALLY PURE OXYGEN AD THE SOLE SOURCE OF FREE OXYGEN AT ATEMPERATURE ABOVE ABOUT 2250*F. IN RELATIVE PROPORTIONS SUCH THAT THECARBON CONTIENT OF SAID FUEL IS SUBSTANTIALLY COMPLETELY CONVERTED TOCARBON MONOXIDE, SUBJECTING ADDITIONAL FOSSIL CARBONACEOUS FUEL TOREACTION WITH AIR IN A SECOND REACTION ZONE AT A TEMPERATURE ABOVE ABOUT2250*F. IN RELATIVE PROPORTIONS SUCH THAT THE CARBON CONTENT OF SAIDFUEL IS SUBSTANTIALLY COMPLETELY CONVERTED TO CARBON MONOXIDE, FORMING AMIXTURE CONTAINING CARBON MONOXIDE AND NITROGEN; COMBINING THE PRODUCTSOF SAID REACTIONS COMPRISING CARBON MONOXIDE AND NITROGEN TOGETHER WITHANY HYDROGEN CONCEMITANTLY PRODUCED IN RELATIVE PROPORTIONS SUCH THATTHE COMPOSITE STREAM CONTAINS AT LEAST THREE VOLUMES OF CARBON MONOXIDEAND HYDROGEN PER VOLUME OF NITROGEN; SUBSEQUENTLY CONVERTING CARBONMONOXIDE IN SAID COMPOSITE STREAM SUSBTANTIALLY COMPLETELY TO CARBONDIOXIDE BY REACTION WITH STEAM THEREBY PRODUCING HYDROGEN; AND REMOVINGSTEAM AND CARBON OXIDES FROM THE RESULTING GAS STREAM THEREBY PRODUCINGA GASEOUS MIXTURE BY HYDROGEN AND NITROGEN CONTAINING APPROXIMATELYTHREE VOLUMES HYDROGEN PER VOLUME OF NITROGEN.